INTERACTION OF CELLULAR PROTEINS WITH THE POLIOVIRUS-5' NONCODING REGION

The 5' noncoding region (NCR) of poliovirus RNA is folded into a compl ex structure comprised of multiple, critically spaced, stem-loop domai ns. Mutations in at least one of these domains markedly affects the ne urovirulence of the virus. Two proteins have been identified recently which bind and apparently mediate functions of the 5' NCR in translati on. We have demonstrated specific binding of three additional proteins in a Hela cell ribosomal salt wash that can be crosslinked to specifi c stem-loop segments of the 5' NCR. These same RNA segments inhibit tr anslation of polio RNA in vitro, presumably by competing for protein b inding. The Sabin vaccine strain of polio RNA exhibits a reduced affin ity of binding for specific proteins. The determinant for this reducti on appears to be a single nucleotide difference at position 480 betwee n the neurovirulent and attenuated viral strains.